Authors:T. Tojo, T. Atake, T. Mori, and H. Yamamura
The heat capacity of 9.70 and 11.35 mol% yttria stabilized zirconia ((ZrO2)1–x(Y2O3)x; x=0.0970, 0.1135) was measured by adiabatic calorimetry between 13 and 300 K, and some thermodynamic functions were calculated and given in a table. A large excess heat capacity extending from the lowest temperature to room temperature with a broad maximum at about 75 K was found in comparison with the heat capacity calculated from those of pure zirconia and yttria on the basis of simple additivity rule. The shape of the excess heat capacity is very similar to the Schottky anomaly, which may be attributed to a softening of lattice vibration. The amount of the excess heat capacity decreased with increasing yttria doping, while the maximum temperature did not vary. The relationships among the excess heat capacity, defect structure and interatomic force constants, and also the role of oxygen vacancy were discussed.
Excess enthalpies and excess isobaric heat capacities of binary mixtures consisting of acetonitrile, dimethylformamide and benzene were measured at 298.15 K. Excess enthalpy of acetonitrile + benzene is positive and that of acetonitrile + dimethylformamide is negative. That of dimethylformamide + benzene is positive and nearly equals to zero as shown in the previous report . Excess heat capacities of acetonitrile + benzene and benzene + dimethylformamide change sign from negative to positive with increase of benzene. That of acetonitrile + dimethylformamide is not simple. It is slightly positive near both ends of mole fraction and not so large negative in the middle of mole fraction. The curve tends to flatten in that region.
Excess isobaric heat capacities of mixture (2-methoxyethanol+water) were measured at T=298.15 K and excess enthalpies at T=293.15 and 298.15 K. Excess enthalpies were extremely exothermic, up to -1290 J mol-1 atT=293.15 K and -1240 J mol-1 at T=298.15 K. Excess isobaric heat capacities were positive and very large, approximately 9 J K-1 mol-1 at the maximum. In contrast to the data reported by Page and coworkers, the excess heat capacity data were positive in the
entire composition range and there was no change in their signs. Consistently, no crossing was found between the curves of
excess enthalpies at T=298.15 and 293.15 K.
Authors:Z. Zhang, M. Zhong, J. Liu, F. Liu, Z. Wang, F. Zhong, and F. Wu
In this work some calorimetric measurements were also carried out on the electrorefining silver by using different current densities with a Calvet type microcalorimeter at room temperature. The ratio (R) of the measured heat (
ex for silver were related with the current density or cell voltage employed in the experiment. The results obtained here also indicate that the heat generation under different conditions, such as different currents or voltages may be caused partially by the irreversibility of the process or by some unknown processes.
The molar excess enthalpies of binary mixtures of pyridine with C6–C9n-alkanes have been measured at 313.15 K in the entire composition range. The measuredHE values were compared with those calculated by means of the Prigogine-Flory-Patterson theory and by the ERAS method.
Authors:Julen Ibarretxe, Gabriël Groeninckx, and Vincent B. F. Mathot
a correction curve from the actual DSC curve, only the heat flow due to the excessheat capacity as caused by phase transitions in the polymer would remain. Such a correction curve has been named “baseline” in literature [ 33 ].
Excess enthalpies, excess heat capacities, excess volumes and sound velocities of the mixture of dioxane isomers, 1,3-dioxane
and 1,4-dioxane, were measured. One of the isomers, 1,4-dioxane is considered as non-polar liquid and the other as polar liquid.
Excess enthalpies are positive and small, less than 55 J mol-1. Excess heat capacities are also very small and the curve is W-shaped, and the values are from 0.03 to -0.08 J mol-1 K-1. Excess volumes and excess isentropic compressibilities are small and positive, and less than 0.03 cm3 mol-1 and 0.8 TPa-1.
Authors:S. Takai, T. Nakanishi, T. Tojo, H. Kawaji, T. Atake, and T. Esaka
Heat capacity measurements were carried out on Pb1-xLaxWO4+x/2 (x=0.2) and Pb1-xLa2x/3WO4 (x=0.2, 0.5) solid solutions prepared by sintering and mechanical alloying (MA) methods. For all the solid solutions, sintered
samples showed slightly larger heat capacity around 100 K in comparison with MA samples, which was presumably caused by the
excitation of mobile oxide ion motion. For sintered scheelite-type structured PbWO4s, high-temperature synthesis introduced oxide ion interstitials even for the Pb1-xLa2x/3WO4 system, which resulted in the excess heat capacity at low temperature for excitation. On the other hand, for the samples
prepared by room-temperature MA technique, oxide ion seemed to occupy the regular sites rather than interstitial ones and
excess heat capacities were not observed.